A review of certain aspects of the background of the invention provides insight into how the invention operates and the benefits provided by the invention. A discussion of the use and limitations of electronic sighting equipment for firearms is presented, followed by a discussion of the operation of semiautomatic firearms and then by an overview of the theory and application of electromagnetic induction.
Firearm Sights
Operators of firearms traditionally used “iron sights” to designate their targets. These iron sights generally consist of a blade or post attached at the muzzle end of the firearm's barrel and a peephole or notch sight at the breech end of the firearm's barrel. Iron sights have certain disadvantages and are often replaced or augmented with newer types of sights, such as laser sights, red-dot/reflex sights, and holographic sights, which provide advantages such as allowing the shooter to more precisely designate the target, allowing the shooter to keep both eyes open while locating the target (meaning the shooter has a better field of view of his/her surroundings while operating the firearm), and reducing the amount of time it takes the shooter to properly designate the target. Iron sights, unless they are augmented by certain equipment, such as tritium inserts, are difficult to use in low light levels or at night; consequently, night-vision equipment or infrared laser sights must be attached to the firearm so that the shooter may use the firearm in such conditions.
Although the alternative sights and sighting equipment described above provide notable improvements over iron sights, they generally take the form of electronic devices which must draw power from either installed batteries or an external power unit (one notable exception is the ACOG, or Advanced Combat Optical Gunsight, which uses a tritium insert for illumination purposes). The sight or sighting equipment will fail to operate without this power source, rendering it useless and either requiring the shooter to return to using the firearm's iron sights or to replace the power source of the sight. Considering that some firearms, such as the M-4 flattop carbine, may have no iron sights whatsoever and may rely solely on electronic sighting equipment, it is imperative that the shooter have an adequate source of back-up power should the power source powering the sighting equipment fail. If the shooter is a combat soldier relying on a piece of electronic sighting equipment, failure to carry a source of back-up power could leave the soldier stranded in the field with a firearm which he cannot properly aim. This situation could lead to tragic results for the soldier or his unit.
Automatic Firearm Operation
Automatic firearms use a portion of the expanding gas from the burning of the gunpowder in a cartridge to provide kinetic energy which moves parts of the firearm to eject the spent casing from the fired cartridge and to load a new cartridge into the firing chamber of the firearm.
Automatic firearms perform this operation through several methods, including the following two relevant methods:
(1) the “recoil operation” method, based upon Newton's Third Law of Motion, in which the force of the expanding propellant gas pushing against the bullet also operates to move the bolt, thereby ejecting the spent casing and loading a new cartridge into the firing chamber, and
(2) the “gas actuation” method, in which a portion of the propellant gas is diverted from the firearm's barrel and acts upon components of the firearm, such as a piston, which then act to move the bolt, thereby ejecting the spent casing and loading a new cartridge into the firing chamber.
Generally, automatic pistols use recoil operation (although some exceptions exist, such as the Heckler & Koch P-7 pistol) while automatic rifles use gas actuation (again, exceptions exist).
Rifles using gas actuation are usually of two types:
(1) those which use a piston to transfer the energy from the expanding gas to move the bolt backwards, a system found in the M-1 Garand, AK-47 and its derivatives, and certain Heckler & Koch rifles, including the G-36 and XM-8, and
(2) those which use a direct impingement method in which the gas is diverted from the barrel, through a gas tube, and directly acts against the bolt or a bolt carrier assembly to move the bolt backwards, a system found on the AR-15 rifle and its derivatives.
The description of an embodiment of the invention in this application shall be described for its embodiment in the AR-15 rifle (which includes the M-16 and M-4 military rifles), although the invention can be applied to firearms which use either the gas actuation method or the recoil operation method.
Electromagnetic Induction
An embodiment of the invention uses the principle of electromagnetic induction to transform the energy of the propellant gas of a fired cartridge, as it operates on the mechanical parts of the firearm, to produce an electric current which is then stored in a capacitor, battery, or other device for the storage of electric energy.
Under the principle of electromagnetic induction, an electric current will flow in a closed conductor, such as a loop of copper wire, when the magnetic flux through the plane bounded by the closed conductor changes. This current will be caused by either a change in the magnitude of the magnetic flux or if the bounded area is moved through the magnetic flux. If the closed conductor is a loop of conductive wire, or a wire formed into a group of loops, the electromotive force (“EMF”) induced by the change of the magnetic flux is determined by Equation 1:ε=−(N)*(dΦ/dt)
In Equation 1, epsilon (“ε”) is the EMF in volts, “N” is the number of loops of the conductive wire, “t” is time in seconds and phi (“Φ”) is the magnetic flux in units of volt-seconds (V*s, or webers). According to the equation, the induced EMF is directly proportional to both the number of loops of wire and the rate of change of the magnetic flux; hence, a greater EMF results for a greater number of loops of wire.
Electromagnetic induction is the basis of electric generators and alternators (generators which produce an alternating current). If a mechanical assembly moves a magnet's position relative to a set of loops of wire, or moves a set of loops of wire relative to a magnet, the assembly causes a current to flow in the wire; the assembly thus acts as a transducer turning the mechanical motion of the assembly into an electromotive force.
One notable consumer electronics device which is based upon the principle of electromagnetic induction is the “Faraday flashlight,” fully described by U.S. Pat. No. 6,994,450; No. 6,893,141; No. 6,808,288; and No. 6,729,744.